﻿//C#中，& 和 &&
List<string> list = null;
if(  list!=null && list.Count > 0)
{
    Console.WriteLine("list 里面有东西");
}
else
{
    Console.WriteLine("list 里面没东西");
}

//https://cloud.tencent.com/developer/information/C%23%E4%B8%AD%26%E5%92%8C%26%26%E8%BF%90%E7%AE%97%E7%AC%A6%E4%B9%8B%E9%97%B4%E7%9A%84%E5%8C%BA%E5%88%AB%E6%98%AF%E4%BB%80%E4%B9%88-video